The Basics
Announced with the D90, the 18-105mm rounds out a full line of 18-xx consumer zooms from Nikon. The xx choices are now 55, 70, 105, 135, and 200mm. The 18-105mm doesn't exactly replicate any equivalent film or FX sensor lens, as it is effectively the DX equivalent of a 28-160mm on those larger capture area cameras. Historically, this isn't quite in the superzoom range, but it's close (the first so called superzoom was 28-200mm).

A wide range of focal lengths is very useful, of course, as it means not taking the lens off and on the camera except when you need something special, such as really wide angle coverage, faster lens aperture, macro coverage, or very long reach telephoto capability. The question when presented with a full lineup of zooms, of course, is which of these 18-xx lenses has the most useful set of features. I'll cut two out of the competition: the 18-70mm and the 18-135mm. That's because neither has VR, and both have one significant optical flaw that can be disruptive and force you to another lens faster (vignetting and chromatic aberration, respectively). As you'll notice, that leaves the very small 18-55mm VR, the very expensive 18-200mm VR, and the lens of this review. You might therefore be able to guess at what I'm about to write: the 18-105mm is probably the Goldilocks choice of the bunch (that's "just right" for those of you not up to snuff on your fairy tales).

Nikon doesn't claim VR II on this lens, and their claims for extra stops of handholdibility seem to indicate that it isn't VR II (3 stops instead of 4). I don't think is any particular issue of note, but it once again calls up that Nikon hasn't done a very good job of differentiating what the VR and VR II differences are. VR can only be turned on and off on this lens; there is no active mode.

The 18-105mm has a hybrid AF-S system, you can sometimes override the focus manually, though the camera will fight you on this more than it does on those lenses with an A/M and M switch (the 18-105mm has only an A and M switch). The focus ring itself is closest to the body, the style of most recent consumer Nikkor zooms.

Both switches are on the left side of the lens as you're holding the camera.

The 18-105mm is an internally focusing lens, so the front element doesn't rotate during zoom or focus. Close focus is okay but not great at 1.5' (.45m), giving a maximum reproduction ratio of about 1:5. The lens design features a single aspherical and ED element for optical corrections. The lens uses 67mm, which appears to be Nikon's new consumer standard filter size.

The lens is made in Thailand.

Handling
The size of the 18-105mm is virtually identical to the 18-135mm when collapsed. It's obviously a little shorter fully extended. As you zoom towards the telephoto end, a double barrel nest extends the front of the lens outwards, not quite doubling its length. The nested barrels on my sample have a fair amount of side to side wiggle possible when fully extended, but I've yet to see this be a problem in images (you generally don't hold the lens by that part and thus don't push it to a side, misaligning the optics, but it's possible).

On my sample of the lens the focus ring is loose but reasonably smooth, while the zoom ring is almost perfect (smooth with no hitches). Full zooming takes only a quarter of a turn of the ring. My sample does not show any tendency to lens creep (zoom without user action when pointed up or down). The butterfly hood (supplied) is a bayonet type that can reverse onto the lens when not in use.

The maximum aperture changes with focal length about as follows:

18mm = f/3.5

24mm = f/4

35mm = f/4.5

50mm = f/5

70mm = f/5.3

85mm+ = f/5.6

Both the front and rear element of the lens are close to the ends when the lens is at 18mm (i.e. they are not inset and protected by the lens barrel or mount).

Performance
Consider that this is a budget lens when you read the following.

Autofocus: As you might expect from an AF-S lens, focus performance is generally fast and direct. I did see just a little bit of a hitch in low light that I don't see with the more expensive AF-S lenses, but not enough to quantify.

Sharpness: As with most of the DX consumer zooms, the 18-105mm is sharp to very sharp in the center, even wide open. It has slightly better performance one stop down, but not enough to avoid maximum aperture. Also like most of the other DX consumer zooms, the corners are weakest at the widest and longest focal lengths and pretty good otherwise. The corners never get terrible, but they barely rise above what I'd call average at 18mm. By 24mm, I'd rate them very good. At 105mm the corners are noticeably soft, but still usable. Overall, the lens seems well matched to the performance of the D90 (and D300) sensor: it's fully capable of resolving to the sensor's ability in the central area. Corners are tough to assess on most lenses via test charts because of curvature of field, but in the shooting I've done with the lens, I'd say that, other than 18mm wide open, the lens reaches the very good range or better in practical use. Considering the price, this is very good bang for the buck.

18mm f/3.5 center:

18mm f/3.5 outer:

105mm f/5.6 center:

105mm f/5.6 outer:

Light falloff: Simple answer: avoid the maximum aperture and vignetting performance is quite good (less than a half stop). At the widest aperture vignetting is about a stop worst case at the extreme focal lengths, much less in between. Wide open is not great performance (note the changes in the test charts, above), but it's not particularly problematic, either. Stopped down performance is quite good for a low-cost consumer lens, indeed, for most lenses.

18mm f/3.5:

105mm f/5.6:

Chromatic aberration: This lens has one of the more consistent chromatic aberration patterns I've seen in testing. Imatest reports between 1 and 1.5 pixels of transition at virtually every aperture and focal length. This is modest but not invisible levels of CA. However, the D90, D300, and Capture NX2 can all correct for this lateral chromatic aberration very easily.

Flare: Flare is decently controlled; I have no real complaints here, though it isn't quite as good as the best of the DX consumer zooms.

Distortion: If this lens has a weak point, it is in linear distortion. At 18mm the barrel distortion is quite pronounced and very visible. It measures over 3.5% on my lens. 24mm is about perfect. From 35mm and up there is substantive but not excessive pincushion distortion measuring the 1-2% range. The distortions seem to be simple, so should be relatively correctable with post processing software.

18mm:

105mm:

Bokeh: I've not noticed anything remarkable either way about the bokeh.

For its price, this is actually quite a well rounded lens. The most visible fault for most will be the barrel distortion at 18mm and perhaps some softness in the corners at 18mm and f/3.5. Beyond that, it falls into what I'd call the "very good and no noticeable flaws" range on almost everything.

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